Reduction of pore fill material dewetting

ABSTRACT

In one exemplary embodiment, a method includes: providing a structure having a first layer overlying a substrate, where the first layer includes a dielectric material having a plurality of pores; applying a filling material to a surface of the first layer, where the filling material includes a polymer and at least one additive, where the at least one additive includes at least one of a surfactant, a high molecular weight polymer and a solvent; and after applying the filling material, heating the structure to enable the filling material to at least partially fill the plurality of pores uniformly across an area of the first layer, where heating the structure results in residual filling material being uniformly left on the surface of the first layer.

TECHNICAL FIELD

The exemplary embodiments of this invention relate generally tosemiconductor devices and, more specifically, relate to porousdielectric materials.

BACKGROUND

This section endeavors to supply a context or background for the variousexemplary embodiments of the invention as recited in the claims. Thecontent herein may comprise subject matter that could be utilized, butnot necessarily matter that has been previously utilized, described orconsidered. Unless indicated otherwise, the content described herein isnot considered prior art, and should not be considered as admitted priorart by inclusion in this section.

It is widely known that the speed of propagation of interconnect signalsis one of the most important factors controlling overall circuit speedas feature sizes are reduced and the number of devices per unit areaincreases. Throughout the semiconductor industry, there is a strongdrive to reduce the dielectric constant (k) of the interlayer dielectric(ILD) materials such as those existing between metal lines, for example.As a result of such reduction, interconnect signals travel fasterthrough conductors due to a concomitant reduction inresistance-capacitance (RC) delays.

Porous ultra low-k (ULK) dielectrics have enabled capacitance reductionin advanced silicon complementary metal-oxide semiconductor (CMOS) backend of line (BEOL) structures. However, the high levels of porosityrequired (e.g., to achieve k values of 2.4 and lower) create issue interms of dielectric material damage or loss due to plasma exposures(e.g., reactive ion etch (RIE), strip, dielectric barrier etch) and wetcleans (e.g., post RIE dilute hydrofluoric acid (DHF) cleans).Additionally, penetration of metals used in the liner layer (e.g., Ta,TaN) or the seed layer (e.g., Cu, Ru) into the pores of the dielectriccan occur when porosity is high and the material is characterized by ahigh degree of pore connectivity. This leads to degradation of thedielectric break down strength and degradation of the leakagecharacteristics of the dielectric. All of these issues collectively maycause reliability and performance degradation in BEOL structures madeusing highly porous ULK dielectrics.

Although the design of a low-k dielectric material with desirableproperties for implementation is demanding enough, the complexity ofmodern semiconductor manufacturing processes adds further complications.Some of these are a direct result from trying to utilize SiO₂-basedprocesses with porous, low-k dielectric materials that are considerablyless forgiving. In this regard, adding porosity may not result inredeeming values (e.g., improved characteristics) other than loweringthe dielectric constant. Critical damage to the low dielectric porousmaterial can occur at different stages of the integration process,including: hard-mask deposition, reactive ion etch, photoresist strip,liner deposition, chemical mechanical polishing, and cap deposition, asnon-limiting examples.

BRIEF SUMMARY

In one exemplary embodiment of the invention, a method comprising:providing a structure comprising a first layer overlying a substrate,where the first layer comprises a dielectric material having a pluralityof pores; applying a filling material to a surface of the first layer,where the filling material comprises a polymer and at least oneadditive, where the at least one additive comprises at least one of asurfactant, a high molecular weight polymer and a solvent (e.g., a highboiling point solvent); and after applying the filling material, heatingthe structure to enable the filling material to at least partially fillthe plurality of pores uniformly across an area of the first layer,where heating the structure results in residual filling material beinguniformly left on the surface of the first layer.

In another exemplary embodiment of the invention, a program storagedevice readable by a machine, tangibly embodying a program ofinstructions executable by the machine for performing operations, saidoperations comprising: providing a structure comprising a first layeroverlying a substrate, where the first layer comprises a dielectricmaterial having a plurality of pores; applying a filling material to asurface of the first layer, where the filling material comprises apolymer and at least one additive, where the at least one additivecomprises at least one of a surfactant, a high molecular weight polymerand a solvent (e.g., a high boiling point solvent); and after applyingthe filling material, heating the structure to enable the fillingmaterial to at least partially fill the plurality of pores uniformlyacross an area of the first layer, where heating the structure resultsin residual filling material being uniformly left on the surface of thefirst layer.

In a further exemplary embodiment of the invention, a method comprising:providing a structure comprising a first layer overlying a substrate,where the first layer comprises a dielectric material having a pluralityof pores; applying a filling material to a surface of the first layer,where the filling material comprises a polymer and at least oneadditive, where the at least one additive comprises at least one of asurfactant, a high molecular weight polymer and a solvent having aboiling temperature between 100° C. and 300° C., where the at least oneadditive is operable to raise a dewet start temperature of the fillingmaterial, where the dewet start temperature is a temperature at whichthe surface of the first layer begins to dewet, where the at least oneadditive is thermally removable, where the high molecular weight polymerhas a molecular weight about or greater than 2000 g/mol, where the atleast one additive is selected based on one or more of: a thickness ofthe first layer, the dielectric material, the filling material, atemperature used to heat the structure and enable the filling materialto at least partially fill the plurality of pores, a heating time, andpore size of the plurality of pores; and after applying the fillingmaterial, heating the structure to enable the filling material to atleast partially fill the plurality of pores uniformly across an area ofthe first layer, where heating the structure results in residual fillingmaterial being uniformly left on the surface of the first layer.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

The foregoing and other aspects of embodiments of this invention aremade more evident in the following Detailed Description, when read inconjunction with the attached Drawing Figures, wherein:

FIG. 1 shows a flowchart illustrating one non-limiting example of amethod for practicing the exemplary embodiments of this invention;

FIGS. 2-8 show a semiconductor wafer at various stages of processing inpracticing the exemplary method depicted in FIG. 1;

FIG. 9 shows a semiconductor structure wherein dewetting occurs whenportions of the surface of the dielectric are exposed after filling thepores with the filling material;

FIG. 10 shows one exemplary embodiment of the invention that avoids thedewetting of FIG. 9 by including at least one additive in the fillingmaterial;

FIG. 11 shows experimental evidence for exemplary embodiments of theinvention whereby a surfactant is added to the filling material;

FIG. 12 shows experimental evidence for exemplary embodiments of theinvention whereby a solvent (e.g., a high boiling point solvent) isadded to the filling material;

FIG. 13 shows experimental evidence for exemplary embodiments of theinvention whereby a solvent (TEG), a surfactant (Pluronic P85) and botha solvent and a surfactant (TEG+Pluronic P85) are added to the fillingmaterial;

FIG. 14 shows analysis data for two porous films, POCS-1 and POCS-2,used in various descriptive examples;

FIG. 15 shows data for six examples, at least some of which are inaccordance with the exemplary embodiments of the invention;

FIG. 16 depicts a flowchart illustrating one, non-limiting example of amethod, and execution of program instructions, for practicing theexemplary embodiments of this invention; and

FIG. 17 depicts a flowchart illustrating another, non-limiting exampleof a method, and execution of program instructions, for practicing theexemplary embodiments of this invention.

DETAILED DESCRIPTION

One technique for addressing the above-noted issues is to fill the poresof the dielectric with a filling material (e.g., a polymer). One priorart technique, as disclosed by U.S. Pat. No. 6,703,324, introduces asecondary component into the void fraction of a porous medium (lowdielectric constant film) in order to temporarily improve the mechanicalproperties such that the porous film has mechanical characteristics of amuch stiffer film. Once a process operation such as a chemicalmechanical polishing process, which requires greater mechanical strengththan that provided by the porous film alone, is completed, the secondarycomponent is removed by displacement or dissolution. Another prior arttechnique, as disclosed by U.S. Pat. No. 7,303,989, impregnates thepores of a zeolite low-k dielectric layer with a polymer and forms aninterconnect structure therein. This mechanically strengthens thedielectric layer and prevents metal deposits within the pores.

Reference is made to commonly-assigned U.S. patent application Ser. No.13/010,004, filed Jan. 20, 2011, concerning porous dielectric fillmethods, techniques, devices, structures and aspects thereof.

Below, and with reference to FIGS. 1-8, is described one, non-limitingexemplary embodiment illustrating how filling the pores of a porousdielectric film (e.g., a low-k or ULK dielectric film) may be beneficialfor processing carried out on the wafer. FIG. 1 depicts a flowchartillustrating one non-limiting example of such a method and is furtherreferred to below with reference to FIGS. 2-8. It is noted that thedescribed exemplary method is for forming a single damasceneinterconnect structure. In other exemplary embodiments, a differentstructure may be formed and/or utilized.

In FIG. 2 (step 101 of FIG. 1), a semiconductor wafer 200 that has aprevious interconnect layer 212 deposited on top is first coated with anILD layer 210 of a porous material containing empty pores (e.g., anorganosilicate), for example, deposited by the best known techniques. Asan example, the interconnect layer 212 may be suitably formed of singleor dual damascene wiring with a high electrical conductivity material(e.g., copper, aluminum, alloys thereof) embedded in a suitable ILD(porous or nonporous) and optionally capped with a diffusion barrierdielectric (e.g., SiN, NBLoK). Detailed make up of layer 212 is omittedin FIGS. 2-8 for purposes of clarity.

In FIG. 3 (step 102 of FIG. 1), the pores of the porous dielectric arefilled with a filling material (e.g., an organic polymer 214) bydepositing the filling material on the porous dielectric and heating thefilling material above the glass transition temperature (Tg) to allow itto flow into the pores. There is an excess layer of the polymer 214 thatforms at the surface of the filled ILD film 230.

In FIG. 4 (step 103 of FIG. 1), the excess of organic polymer 214 thatwas deposited on top of the filled ILD film 230 is then removed by asuitable method, such as plasma etch, RIE strip, wet dissolution orgentle polishing. Care should be exercised not to remove the polymerfrom the filled pores in the structure.

In FIG. 5 (step 104 of FIG. 1), a hardmask layer 216 is deposited on topof the filled ILD layer 230, for example, using plasma enhanced chemicalvapor deposition (PECVD) or spin-on techniques. The hardmask 216 can beformed of any suitable material including, as non-limiting examples,SiO₂, Al₂O₃, SiN, Si₃N₄, SiC, SiCOH or another suitable hardmaskmaterial as known in the art. The hardmask layer 216 may further beformed by more than one layer of material, though the total thicknesspreferably should be less than 250 nm and, more preferably, less than100 nm.

In step 105 of FIG. 1, a photoresist layer is applied to the top of thehardmask layer 216, exposed to generate a desired pattern, developed andthen baked (e.g., at a temperature on the order of 200° C. or less).

In step 106 of FIG. 1, the hardmask layer 216 and the filled ILD layer230 are etched (e.g., in a plasma etching process) to remove them inthose regions defined by openings in the photoresist pattern on top ofthe hardmask layer 216.

In step 107 of FIG. 1, any remnants of the resist layer are removed by astrip process. It should be noted that this is the step where theporosity of the organosilicate is exposed to the strip process chemistryused to remove the photoresist and damage would otherwise occur to thepores of the filled ILD layer 230 if they were not filled with thepolymer. Without first filling the pores, after such an exposure thedielectric constant and the leakage current of the ILD increasesignificantly. In contrast, as the ILD is in a nonporous hybrid stateenriched in carbon due to the fill material now present in the originalpores, little or no damage occurs to the filled ILD layer 230.

In step 108 of FIG. 1, a liner material is deposited to form a linerlayer 222 on top of the hardmask layer 216. The liner layer 222 may becomprised of a material such as TaN, TiN, Ti, Ta, or variouscombinations thereof, as non-limiting examples, for achieving adhesionand diffusion barrier properties.

At this stage, in some exemplary embodiments a seed layer (e.g., copper)is deposited on top of the liner layer 222. The seed layer may bedeposited by sputtering, for example, and may be used to facilitatesubsequent electroplating.

In step 109 of FIG. 1, the etched opening is filled with a metal 224,such as copper, for example. The metal may be formed by electroplating,for example, and overfills the opening.

In step 110 of FIG. 1, after the etched opening is filled with the metal224, the electronic structure 200 is planarized (e.g., by a chemicalmechanical polishing (CMP) process) to achieve a planar surface with ametal inlaid structure. In this CMP step, polishing is performed untilall of the excess metal, liner and hardmask on top of the filled ILDlayer 230 are removed, thus exposing at least a top surface of thefilled ILD layer 230.

FIG. 6 shows the electronic structure 200 after performance of steps105-110 noted above.

In FIG. 7 (step 111 of FIG. 1), the filling material (e.g., the organicpolymer) is removed from the pores, for example, by decomposing it usinga thermal curing or a thermal curing assisted by ultraviolet (UV)irradiation, as non-limiting examples.

In FIG. 8 (step 112 of FIG. 1), a cap layer 226 of an insulatingmaterial (e.g., silicon carbide, silicon nitride, silicon carbonitride,combinations thereof) is deposited on top in order to prevent diffusionof the metal and to protect the electronic device 200 (e.g., frommechanical abrasion or other damage).

As described above, by filling the pores of the porous ILD (e.g., with apolymer), damage to the ILD (e.g., to the pores of the ILD) can beavoided during processing of the structure. Also as noted above, much ofthe potential for damage stems from the strip process chemistry used toremove the photoresist. Without filling the pores, the dielectricconstant and the leakage current of the ILD may be adversely affected(e.g., significantly increased). Generally, when filling the porousdielectric with the filling material it is desirable to achieve uniformcoverage (e.g., full, even coverage across the surface of the dielectricresulting in an even, continuous film) with the deposited fillingmaterial in order to obtain homogeneous filling of the pores(substantially even distribution of the filing material throughout thethickness of the porous material).

In view of this goal, it is further desirable to avoid dewetting of thefilling material during filling of the porous material. As shown in FIG.9, and as a non-limiting example, dewetting occurs when portions of thesurface of the dielectric are exposed after filling the pores with thefilling material (e.g., a polymer). In FIG. 9A, a porous ILD 310 isshown disposed over a substrate 312. In FIG. 9B, the structure is coatedwith a polymer 314 that will be used to fill the pores. In FIG. 9C, thepolymer is heated above its glass transition temperature (Tg) to enableit to fill the pores (yielding a filled porous dielectric 330). As canbe seen in FIG. 9C, this operation results in exposure of a portion ofthe surface of the ILD 332. In FIG. 9D, the excess polymer on thesurface of the ILD is removed by a suitable means. Since there isnon-uniform coverage by the excess polymer, the removal of the excesspolymer from the surface of the ILD also removes the polymer from someof the pores resulting in inhomogeneous filling of the pores 334.Clearly this is not a desirable result. Furthermore, this may lead thestructure to be incompatible with integration.

Various prior art documents have considered dewetting of polymer films,including:

-   (A) K. A. Barnes et al. Suppression of Dewetting in    Nanoparticle-Filled Polymer Films, Macromolecules 2000, 33,    4177-4185;-   (B) M. E. Mackay et al. Influence of Dendrimer Additives on the    Dewetting of Thin Polystyrene Films, Langmuir 2002, 18, 1877-1882;-   (C) J. M. Kropka et al. Control of Interfacial Instabilities in Thin    Polymer Films with the Addition of a Miscible Component,    Macromolecules 2006, 39, 8758-8762;-   (D) D Y Ryu et al. A Generalized Approach to the Modification of    Solid Surfaces, Science 8 Apr. 2005, 308, 236-239;-   (E) S H Choi et al. Suppress polystyrene thin film dewetting by    modifying substrate surface with aminopropyltriethoxysilane, Surface    Science 2006, 600, 1391-1404; and-   (F) I. Luzinov et al. Thermoplastic elastomer monolayers grafted to    a functionalized silicon surface, Macromolecules 2000, 33,    7629-7638.

It is noted that for references A, B and C the structure must be heatedto over 400° C. to decompose the additive and this process leaves aresidue. In contrast, exemplary embodiments of the invention, asdescribed below, comply with dielectric processing and do not requireheating above 425° C. (e.g., above 400° C.) to completely remove allfilling material and additives. Furthermore, exemplary embodiments ofthe invention do not result in residue remaining on the surface inquestion. Preferably, no excess polymer is left on the surface.

For references D, E and F, it is noted that these references consider anon-porous film. They do not discuss porous films. Furthermore, theyanchor the polymer to the film using a chemical bond. In contrast,exemplary embodiments of the invention do not use or require such achemical bond, said chemical bond being undesirable for dielectricprocessing.

Dewetting of the polymer on the low-k dielectric film is observed whenheating above Tg: (a) due to loss of solvent in the polymer filmpresenting unfavorable surface energy interactions; and/or (b) due tonon-entanglement of low molecular weight polymer chains. Surface energyinteractions can be modified by the addition of diluents and/orsurfactants to the polymer.

Exemplary embodiments of the invention use a polymer formulation to fillthe pores of the porous dielectric. The polymer formulation results inuniform coverage by the excess polymer (e.g., across an area of thesurface of the dielectric) and, thus, (substantially) homogeneousfilling of the pores. Furthermore, usage of the polymer formulationavoids dewetting of the excess polymer and yields a structure that iscompatible with integration. FIG. 10 shows one exemplary embodiment ofthe invention that avoids the dewetting of FIG. 9 by including at leastone additive in the filling material. In FIG. 10A, a porous ILD 410 isshown disposed over a substrate 412. In FIG. 10B, the structure iscoated with a polymer 414 that will be used to fill the pores. In FIG.10C, the polymer is heated above its glass transition temperature (Tg)to enable it to fill the pores (yielding a filled porous dielectric430). In FIG. 10D, the residual (e.g., excess) polymer on the surface ofthe ILD is by a suitable means. Since there is uniform coverage by theresidual polymer, the removal of the residual polymer from the surfaceof the ILD does not remove the polymer from any of the pores, resultingin homogeneous filling of the pores.

As noted above, heating the structure enables the filling material to atleast partially fill the plurality of pores uniformly across an area ofthe first layer. The area of the first layer is considered generally tobe a horizontal plane (substantially) perpendicular to the depth orthickness of the first layer. The area of the first layer will, at onepoint, be coincident (roughly/approximately or precisely) with thesurface of the first layer (i.e., the surface to which the fillingmaterial is applied). As is clear, the uniformity considered hereingenerally is across the horizontal plane (e.g., the area) of the firstlayer, both with respect to pore-filling and disposition of the residualpolymer on the surface of the first layer.

As a non-limiting example, the polymer formulation may comprise apolymer (e.g., a low molecular weight polymer) to which at least one ofa surfactant, a high molecular weight polymer and a solvent (e.g., ahigh boiling point solvent) has been added. These additives arethermally removable in order to comply with integration needs. That is,these additives must be removed at the end of the process and thestructure can only be heated up to 425° C. under inert atmosphere.Beyond that temperature, further, desirable components break down.

As referred to herein, a solvent is considered to be a liquid materialthat dissolves another material (a liquid, solid or gaseous solute)resulting in a solution. A high boiling point (HBP) solvent generallyrefers to a solvent that has a boiling point greater than or equal to150° C. (e.g., greater than or equal to 200° C.). A surfactant isconsidered to be a material or compound that lowers the surface tensionof a liquid, the interfacial tension between two liquids or theinterfacial tension between a liquid and a solid. As an example, thesurfactant may comprise an organic compound that is amphiphilic (meaningit contains hydrophobic groups and hydrophilic groups).

As non-limiting examples, the surfactant may be selected from the groupof amphiphilic surfactants comprising block or graft copolymers such aspoly(styrene-co-ethylene oxide), poly(styrene-co-propylene oxide),poly(alkane-co-ethylene oxide), poly(alkane-co-propylene oxide),poly(ether-co-lactones), poly(ester-co-carbonates), poly(ethyleneoxide-co-propylene oxide), poly(ethylene oxide-co-propyleneoxide-co-ethylene oxide) and poly(propylene oxide-co-ethyleneoxide-co-propylene oxide). As further non-limiting examples, the solventmay be selected from the group of polymer compatible diluents with aboiling point higher than the polymer Tg, such as oligo(ethyleneglycols), oligo(propylene glycols), N-methyl pyrrolidone,dimethylformamide, dimethylsulfoxide, g-butyrolactone, cyclohexanone,cyclopentanone, xylenes, mesitylene.

It should be noted that for at least some exemplary embodiments whereinthe at least one additive includes a HBP solvent, the HBP solvent isdifferent from other solvents that may be used such as those used todissolve the polymer, for example. That is, two solvents may be used—afirst in which the polymer is dissolved and a second one acting as theat least one additive (e.g., a HBP solvent). The first solvent willevaporate while the second remains (e.g., due to the higher boilingpoint).

FIG. 11 shows experimental evidence for exemplary embodiments of theinvention whereby a surfactant is added to the filling material. FIG. 12shows experimental evidence for exemplary embodiments of the inventionwhereby a solvent (e.g., a high boiling point solvent) is added to thefilling material. FIG. 13 shows experimental evidence for exemplaryembodiments of the invention whereby a solvent (TEG), a surfactant(Pluronic P85) and both a solvent and a surfactant (TEG+Pluronic P85)are added to the filling material.

In FIGS. 11-13, CA stands for contact angle and is indicative of thehydrophilicity of the surface. A surface is considered hydrophilic ifwater CA is less than 45°, and hydrophobic if water CA is greater than45°. Pluronic®, Tetronic®, Tween® and Brij® are trade names. DPG standsfor di(propylene glycol) and TEG stands for tetra(ethylene glycol). POCSstands for porous oxycarbosilane, the type of porous films used togenerate the examples.

The goal is to raise the temperature at which dewet occurs (e.g., toraise the temperature to be as high as possible). The data only goes upto 250° C. since beyond that temperature the chosen polymer willdegrade. As is apparent from the data of FIG. 13, in at least some casesit is beneficial to use both a solvent and a surfactant. The selectionof which additive(s) to use may be based on one or more of: thethickness of the dielectric, the dielectric material, the polymer fillmaterial, the temperature used to fill the pores with the polymer,heating time, pore size, the process/operations used and/or otherfactors.

As noted above, in some exemplary embodiments a high molecular weight(HMW) polymer is added to the polymer (e.g., a low molecular weight LMWpolymer) which is to penetrate the porosity. Unlike the LMW polymer, theHMW polymer does not penetrate into the porosity and, instead, remainson the surface of the porous dielectric. This allows the LMW polymer tobe heated at a higher temperature in order to promote pore filling,while still avoiding dewet.

As referred to herein, a HMW polymer is considered to be a polymerhaving a molecular weight about or greater than 2000 g/mol (e.g., largerthan 10000 g/mol).

As a non-limiting example, the HMW polymer may comprise a high molecularweight form of polystyrene (e.g., polystyrene with a molecular weight ofabout 9500-10500 g/mol). In some exemplary embodiments, the HMW polymerhas a molecular weight about or greater than 7000 g/mol. In furtherexemplary embodiments, the HMW polymer has a molecular weight about orgreater than 8000 g/mol. In other exemplary embodiments, the HMW polymerhas a molecular weight about or greater than 9000 g/mol. In furtherexemplary embodiments, the HMW polymer has a molecular weight about orgreater than 10000 g/mol.

Below are provided examples to demonstrate the use of exemplary highmolecular weight polymers to prevent dewet (e.g., of a low molecularweight polymer). FIG. 14 shows analysis data for the two porous filmsused, POCS-1 and POCS-2. FIG. 15 shows data for the six examplesconsidered below.

The following solutions were used:

-   -   Poly-1 (Example 1): 5 wt. % poly(methyl methacrylate) (molecular        weight Mw=1100 g/mol) and 0.5 wt. % poly(methyl methacrylate)        (Mw=9900 g/mol) in Propylene Glycol Methyl Ether Acetate.    -   Poly-2 (Example 2): 5 wt. % polystyrene (Mw=1000 g/mol) and 0.5        wt. % polystyrene (Mw=10000 g/mol) in Toluene.    -   Poly-3 (Example 3): 5 wt. % poly(methyl methacrylate) (Mw=1100        g/mol) in Propylene Glycol Methyl Ether Acetate.    -   Poly-4 (Example 4): 5 wt. % polystyrene (Mw=1000 g/mol) in        Toluene.    -   Poly-5 (Example 5): 5 wt. % poly(methyl methacrylate) (Mw=9900        g/mol) in Propylene Glycol Methyl Ether Acetate.    -   Poly-6 (Example 6): 5 wt. % polystyrene (Mw=10000 g/mol) in        Toluene.

The porous films used (referred to as “POCS-1” and “POCS-2”) weresynthesized from the same microelectronic grade formulation composed ofa thermally stable organosilicate oxycarbosilane polymer and a thermallydecomposable organic polymer. POCS-1 and POCS-2 were synthesized byspin-coating the above formulations on 8-inch silicon wafers, applyingfirst a post-applied bake on a hot plate at 85° C. for 2 minutes andthen curing the films in a Yield Engineering Systems Inc. (YES®)polyimide bake oven at 250° C. for 15 minutes using a 5° C./min ramp.The films were then cured at 400° C. for 7 minutes under UV irradiation.The porosities of POCS-1 and POCS-2 were measured by ellipsometricporosimetry using toluene as the adsorbent (Kelvin model). The densityand thickness were obtained using X-ray reflectivity (XRR) and therefractive index using spectral-reflectometry.

The analysis data is summarized in FIG. 14. The only notable differencebetween POCS-1 and POCS-2 is the thickness of the film.

Example 1

Poly-1 was spin-coated on top of POCS-1 at 1000 rpm for 30 seconds.POCS-1 was afterwards heated successively at increasing temperaturesuntil dewet was observed. The results are summarized in FIG. 15.

Example 2

Poly-2 was spin-coated on top of POCS-1 at 1000 rpm for 30 seconds.POCS-1 was afterwards heated successively at increasing temperaturesuntil dewet was observed. The results are summarized in FIG. 15.

Example 3

Poly-3 was spin-coated on top of POCS-2 at 1000 rpm for 30 seconds.POCS-2 was afterwards heated successively at increasing temperaturesuntil dewet was observed. The results are summarized in FIG. 15.

Example 4

Poly-4 was spin-coated on top of POCS-2 at 1000 rpm for 30 seconds.POCS-2 was afterwards heated successively at increasing temperaturesuntil dewet was observed. The results are summarized in FIG. 15.

Example 5

Poly-5 was spin-coated on top of POCS-2 at 1000 rpm for 30 seconds.POCS-2 was afterwards heated at 200° C. for 1 minute; the polymer filmdid not dewet. The excess polymer was then removed and the film wasanalyzed by spectral reflectometry and x-ray reflectivity. Nopenetration of the polymer in the pores was detected.

Example 6

Poly-6 was spin-coated on top of POCS-2 at 1000 rpm for 30 seconds.POCS-2 was afterwards heated at 200° C. for 1 minute; the polymer filmdid not dewet. The excess polymer was then removed and the film wasanalyzed by spectral reflectometry and x-ray reflectivity. Nopenetration of the polymer in the pores was detected.

From these 6 examples, one can see that the addition of a HMW polymer toa LMW polymer enables one to increase the dewet temperature and,further, that the HMW polymer does not penetrate into the pores of theporous film.

Below are further descriptions of various non-limiting, exemplaryembodiments of the invention. The below-described exemplary embodimentsare numbered separately for clarity purposes. This numbering should notbe construed as entirely separating the various exemplary embodimentssince aspects of one or more exemplary embodiments may be practiced inconjunction with one or more other aspects or exemplary embodiments.

(1) In one exemplary embodiment of the invention, and as shown in FIG.16, a method comprising: providing a structure comprising a first layeroverlying a substrate, where the first layer comprises a dielectricmaterial having a plurality of pores (601); applying a filling materialto a surface of the first layer, where the filling material comprises apolymer and at least one additive, where the at least one additivecomprises at least one of a surfactant, a high molecular weight polymerand a solvent (602); and after applying the filling material, heatingthe structure to enable the filling material to at least partially fillthe plurality of pores uniformly across an area of the first layer,where heating the structure results in residual filling material beinguniformly left on the surface of the first layer (603).

A method as above, where the at least one additive is operable to raisea dewet start temperature of the filling material, where the dewet starttemperature is a temperature at which the surface of the first layerbegins to dewet. A method as in any above, where the at least oneadditive is operable to reduce or eliminate dewetting of the excessfilling material. A method as in any above, where the at least oneadditive is thermally removable. A method as in any above, where the atleast one additive comprises a solvent having a boiling temperaturebetween 100° C. and 300° C. A method as in any above, where the at leastone additive comprises a solvent having a boiling temperature between150° C. and 250° C.

A method as in any above, where the at least one additive comprises ahigh molecular weight polymer that is too large to penetrate the poresof the dielectric material. A method as in any above, where the at leastone additive comprises a high molecular weight polymer having amolecular weight about or greater than 2000 g/mol. A method as in anyabove, where the at least one additive comprises a high molecular weightpolymer having a molecular weight about or greater than 10000 g/mol. Amethod as in any above, where the at least one additive is selectedbased on one or more of: a thickness of the first layer, the dielectricmaterial, the filling material, a temperature used to heat the structureand enable the filling material to at least partially fill the pluralityof pores, a heating time, and pore size of the plurality of pores. Amethod as in any above, where the at least one additive comprises thesurfactant. A method as in any above, where the at least one additivecomprises the high molecular weight polymer. A method as in any above,where the at least one additive comprises the solvent. A method as inany above, where heating the structure results in the residual fillingmaterial being uniformly left across an area of the surface of the firstlayer. A method as in any above, where the at least one additivecomprises a solvent having a boiling temperature greater than 150° C.

A method as in any above, implemented as a computer program. A method asin any above, implemented as a program of instructions stored (e.g.,tangibly embodied) on a program storage device (e.g., at least onememory, at least one computer-readable medium) and executable by acomputer (e.g., at least one processor). A method as in any above,further comprising one or more aspects of the exemplary embodiments ofthe invention as described further herein.

(2) In another exemplary embodiment of the invention, a program storagedevice readable by a machine, tangibly embodying a program ofinstructions executable by the machine for performing operations, saidoperations comprising: providing a structure comprising a first layeroverlying a substrate, where the first layer comprises a dielectricmaterial having a plurality of pores (601); applying a filling materialto a surface of the first layer, where the filling material comprises apolymer and at least one additive, where the at least one additivecomprises at least one of a surfactant, a high molecular weight polymerand a solvent (602); and after applying the filling material, heatingthe structure to enable the filling material to at least partially fillthe plurality of pores uniformly across an area of the first layer,where heating the structure results in residual filling material beinguniformly left on the surface of the first layer (603).

A program storage device as in any above, where the program storagedevice comprises at least one memory or at least one computer-readablemedium. A program storage device as in any above, where the machinecomprises a computer or at least one processor configured to execute theprogram of instructions. A program storage device as in any above,further comprising one or more aspects of the exemplary embodiments ofthe invention as described further herein.

(3) In a further exemplary embodiment of the invention, and as shown inFIG. 17, a method comprising: providing a structure comprising a firstlayer overlying a substrate, where the first layer comprises adielectric material having a plurality of pores (701); applying afilling material to a surface of the first layer, where the fillingmaterial comprises a polymer and at least one additive, where the atleast one additive comprises at least one of a surfactant, a highmolecular weight polymer and a solvent having a boiling temperaturebetween 100° C. and 300° C., where the at least one additive is operableto raise a dewet start temperature of the filling material, where thedewet start temperature is a temperature at which the surface of thefirst layer begins to dewet, where the at least one additive isthermally removable, where the high molecular weight polymer has amolecular weight about or greater than 2000 g/mol, where the at leastone additive is selected based on one or more of: a thickness of thefirst layer, the dielectric material, the filling material, atemperature used to heat the structure and enable the filling materialto at least partially fill the plurality of pores, a heating time, andpore size of the plurality of pores (702); and after applying thefilling material, heating the structure to enable the filling materialto at least partially fill the plurality of pores uniformly across anarea of the first layer, where heating the structure results in residualfilling material being uniformly left on the surface of the first layer(703).

A method as in any above, implemented as a computer program. A method asin any above, implemented as a program of instructions stored (e.g.,tangibly embodied) on a program storage device (e.g., at least onememory, at least one computer-readable medium) and executable by acomputer (e.g., at least one processor). A method as in any above,further comprising one or more aspects of the exemplary embodiments ofthe invention as described further herein.

(4) In another exemplary embodiment of the invention, a program storagedevice readable by a machine, tangibly embodying a program ofinstructions executable by the machine for performing operations, saidoperations comprising: providing a structure comprising a first layeroverlying a substrate, where the first layer comprises a dielectricmaterial having a plurality of pores (701); applying a filling materialto a surface of the first layer, where the filling material comprises apolymer and at least one additive, where the at least one additivecomprises at least one of a surfactant, a high molecular weight polymerand a solvent having a boiling temperature between 100° C. and 300° C.,where the at least one additive is operable to raise a dewet starttemperature of the filling material, where the dewet start temperatureis a temperature at which the surface of the first layer begins todewet, where the at least one additive is thermally removable, where thehigh molecular weight polymer has a molecular weight about or greaterthan 2000 g/mol, where the at least one additive is selected based onone or more of: a thickness of the first layer, the dielectric material,the filling material, a temperature used to heat the structure andenable the filling material to at least partially fill the plurality ofpores, a heating time, and pore size of the plurality of pores (702);and after applying the filling material, heating the structure to enablethe filling material to at least partially fill the plurality of poresuniformly across an area of the first layer, where heating the structureresults in residual filling material being uniformly left on the surfaceof the first layer (703).

A program storage device as in any above, where the program storagedevice comprises at least one memory or at least one computer-readablemedium. A program storage device as in any above, where the machinecomprises a computer or at least one processor configured to execute theprogram of instructions. A program storage device as in any above,further comprising one or more aspects of the exemplary embodiments ofthe invention as described further herein.

(5-1) A method for forming a porous dielectric material layer in anelectronic structure comprising the steps of: providing a pre-processedelectronic substrate, forming thereon a layer of fully cured firstporous dielectric material which has achieved its full shrinkage,depositing on top of the porous dielectric material a layer of polymerwith a stabilizing agent, heating the system above the Tg of the polymerto homogeneously fill the porosity without observing dewetting ofpolymer layer on dielectric surface, defining and patterninginterconnect pattern openings in said non-porous dielectric material,filling said interconnect pattern openings with an electricallyconductive material, planarizing said electrically conductive materialby chemical mechanical polishing and heating said electronic substrateto a first temperature high enough to drive out said organic polymerfrom said pores thus transforming said pore-filled dielectric into asecond porous dielectric material where the film structure andcomposition are homogeneous between the bulk and the line sidewalls andbottom, thus indicating little or no plasma damage during processing.(5-2) A method for forming said second porous dielectric material layerin an electronic structure according to 5-1, wherein said first porousdielectric material is substantially made of silicon containingdielectrics selected from the group comprising silicon oxide,methylsilsesquioxane, hydrogensilsesquioxane, oxycarbosilanes andcopolymers thereof.(5-3) A method for forming a second porous dielectric material layer inan electronic structure according to 5-1, wherein said organic polymerused for filling said pores in said first porous dielectric is selectedfrom the group comprising: poly(2-alkyl oxazolines),poly(N,N-dialkylacrylamides), poly(caprolactones), polyesters,polylactides, polystyrenes, substituted polystyrenes, poly-alphamethylstyrene, substituted poly-alpha methyl polystyrenes, aliphaticpolyolefins, polynorbornenes, polyacrylates, polymethacrylates,poly(alkyl oxazolines), polyethers and copolymers thereof. Polymers andcopolymers of polyethylene oxide, polypropylene oxide andpolytetrahydrofuran also may be used.(5-4) A method for forming a second porous dielectric material layer inan electronic structure according to 5-1, wherein said the stabilizingagent used for preventing dewetting of polymer layer on dielectricsurface is selected from the group of amphiphilic surfactants comprisingblock or graft copolymers such as poly(styrene-co-ethylene oxide),poly(styrene-co-propylene oxide), poly(alkane-co-ethylene oxide),poly(alkane-co-propylene oxide), poly(ether-co-lactones),poly(ester-co-carbonates), poly(ethylene oxide-co-propylene oxide),poly(ethylene oxide-co-propylene oxide-co-ethylene oxide) andpoly(propylene oxide-co-ethylene oxide-co-propylene oxide), asnon-limiting examples.(5-5) A method for forming a second porous dielectric material layer inan electronic structure according to 5-1, wherein said the stabilizingagent used for preventing dewetting of polymer layer on dielectricsurface is selected from the group of polymer compatible diluents with aboiling point higher than the polymer Tg, such as oligo(ethyleneglycols), oligo(propylene glycols), N-methylpyrrolidone,dimethylformamide, dimethylsulfoxide, g-butyrolactone, cyclohexanone,cyclopentanone, xylenes, mesitylene.(5-6) A method for forming said second porous dielectric material layerin an electronic structure according to 5-1, wherein said stabilizingagent is introduced in between about 0.5 wt % and about 95 wt %.(5-7) A method for forming said second porous dielectric material layerin an electronic structure according to 5-1, wherein said stabilizingagent is fully decomposable by thermal means at temperatures rangingfrom 300° C. to 450° C.(5-8) A method for forming a porous dielectric material layer in anelectronic structure according to 5-1, further comprising the step offorming a mask layer on top of said layer of non-porous dielectricmaterial.(5-9) A method according to 5-8, wherein said mask layer is made of atleast one material selected from the group consisting of silicon oxide,silicon nitride, silicon carbide, and SiCOH and is deposited at a secondtemperature below said first temperature required to drive out saidorganic polymer from said pores.(5-10) A method for forming a second porous dielectric material layer inan electronic structure according to 5-1, wherein said steps ofpatterning interconnect pattern openings in said non-porous dielectricmaterial, filling said interconnect pattern openings with anelectrically conductive material, and planarizing said electricallyconductive material by chemical mechanical polishing are all performedat temperatures less than said first temperature.(5-11) A method for forming a second porous dielectric material layer inan electronic structure according to 5-1, wherein said first temperaturefor fully curing said first porous dielectric is between about 350° C.and about 450° C.(5-12) A method for forming a second porous dielectric material layer inan electronic structure according to 5-1, wherein the thermal cure isultraviolet (UV) assisted (e.g., to improve the efficiency of thethermal cure).(5-13) A method for forming said second porous dielectric material layerin an electronic structure according to 5-1, wherein said first andsecond porous materials have a porosity of between about 25 vol. % andabout 80 vol. %.(5-14) A method for forming a porous dielectric material layer in anelectronic structure according to 5-1, wherein said first and secondporous dielectric materials preferably have a porosity of between about25 vol. % and about 60 vol. %.(5-15) A structure comprising at least one interconnect metal lineembedded in a porous dielectric wherein the porous regions of saidporous dielectric substantially maintain the same amount of carbon inthe bulk of the film and at the liner, metal and cap interfaces frompatterning, etching and polishing processes and free of any penetrationof said interconnect metal into said porous regions of said porousdielectric.(5-16) A method of forming the structure of 5-15, comprising the stepsof: forming a first porous dielectric material layer that has reachedits maximum shrinkage, depositing on top of the porous dielectricmaterial a layer of polymer with a stabilizing agent, heating the systemabove the Tg of the polymer to homogeneously fill the porosity withoutobserving dewetting of polymer layer on dielectric surface, depositing ahard mask on said nonporous dielectric, patterning a photoresist layeratop said hard mask, etching said hard mask and said nonporous hybriddielectric using a reactive ion etching process, stripping saidphotoresist, depositing a conductive liner and seed and overfilling thestructure with conductive material, removing the excess of saidconductive material, liner, seed and hard-mask using chemical mechanicalpolishing, removing said polymer from said pores in said first porousdielectric and leaving behind a second porous dielectric in the finalstructure which is substantially free of process damage from patterning,etching and polishing processes and free of any penetration of saidinterconnect metal.(5-17) A method according to 5-16, wherein said small enough molecularweight of said polymer is less than 10000 g/mol and more preferably lessthan 5000 g/mol.(5-18) A method according to 5-15 and/or 5-16, wherein said step ofremoving said polymer from said pores in said first porous dielectric isachieved by a process selected from thermal decomposition and UVradiation assisted thermal decomposition.(5-19) A method according to 5-16, wherein said thermal decompositionand said UV radiation assisted thermal decomposition are performed at atemperature of about 300° C. to 450° C.

The exemplary embodiments of the invention, as discussed herein and asparticularly described with respect to exemplary methods, may beimplemented in conjunction with a program storage device (e.g., at leastone memory) readable by a machine, tangibly embodying a program ofinstructions (e.g., a program or computer program) executable by themachine for performing operations. The operations comprise steps ofutilizing the exemplary embodiments or steps of the method.

The blocks shown in FIGS. 16 and 17 further may be considered tocorrespond to one or more functions and/or operations that are performedby one or more components, circuits, chips, apparatus, processors,computer programs and/or function blocks. Any and/or all of the abovemay be implemented in any practicable solution or arrangement thatenables operation in accordance with the exemplary embodiments of theinvention as described herein.

In addition, the arrangement of the blocks depicted in FIGS. 16 and 17should be considered merely exemplary and non-limiting. It should beappreciated that the blocks shown in FIGS. 16 and 17 may correspond toone or more functions and/or operations that may be performed in anyorder (e.g., any suitable, practicable and/or feasible order) and/orconcurrently (e.g., as suitable, practicable and/or feasible) so as toimplement one or more of the exemplary embodiments of the invention. Inaddition, one or more additional functions, operations and/or steps maybe utilized in conjunction with those shown in FIGS. 16 and 17 so as toimplement one or more further exemplary embodiments of the invention.

That is, the exemplary embodiments of the invention shown in FIGS. 16and 17 may be utilized, implemented or practiced in conjunction with oneor more further aspects in any combination (e.g., any combination thatis suitable, practicable and/or feasible) and are not limited only tothe steps, blocks, operations and/or functions shown in FIGS. 16 and 17.

Any use of the terms “connected,” “coupled” or variants thereof shouldbe interpreted to indicate any such connection or coupling, direct orindirect, between the identified elements. As a non-limiting example,one or more intermediate elements may be present between the “coupled”elements. The connection or coupling between the identified elements maybe, as non-limiting examples, physical, electrical, magnetic, logical orany suitable combination thereof in accordance with the describedexemplary embodiments. As non-limiting examples, the connection orcoupling may comprise one or more printed electrical connections, wires,cables, mediums or any suitable combination thereof.

Generally, various exemplary embodiments of the invention can beimplemented in different mediums, such as software, hardware, logic,special purpose circuits or any combination thereof. As a non-limitingexample, some aspects may be implemented in software which may be run ona computing device, while other aspects may be implemented in hardware.

The foregoing description has provided by way of exemplary andnon-limiting examples a full and informative description of the bestmethod and apparatus presently contemplated by the inventors forcarrying out the invention. However, various modifications andadaptations may become apparent to those skilled in the relevant arts inview of the foregoing description, when read in conjunction with theaccompanying drawings and the appended claims. However, all such andsimilar modifications will still fall within the scope of the teachingsof the exemplary embodiments of the invention.

Furthermore, some of the features of the preferred embodiments of thisinvention could be used to advantage without the corresponding use ofother features. As such, the foregoing description should be consideredas merely illustrative of the principles of the invention, and not inlimitation thereof.

What is claimed is:
 1. A method comprising: providing a structurecomprising a first layer overlying a substrate, where the first layercomprises a dielectric material having a plurality of pores; applying afilling material to a surface of the first layer, where the fillingmaterial comprises a polymer and at least one additive, where the atleast one additive comprises at least one of a surfactant, a highmolecular weight polymer and a solvent, and where the at least oneadditive is operable to reduce or eliminate dewetting of excess fillingmaterial; and after applying the filling material, heating the structureto enable the filling material to at least partially fill the pluralityof pores uniformly across an area of the first layer, where heating thestructure results in residual filling material being uniformly left onthe surface of the first layer.
 2. The method of claim 1, where the atleast one additive is operable to raise a dewet start temperature of thefilling material, where the dewet start temperature is a temperature atwhich the filling material on the surface of the first layer begins todewet.
 3. The method of claim 1, where the at least one additive isthermally removable.
 4. The method of claim 1, where the at least oneadditive comprises a solvent having a boiling temperature between 100°C. and 300° C.
 5. The method of claim 1, where the at least one additivecomprises a solvent having a boiling temperature between 150° C. and250° C.
 6. The method of claim 1, where the at least one additivecomprises a high molecular weight polymer that is too large to penetratethe pores of the dielectric material.
 7. The method of claim 1, wherethe at least one additive comprises a high molecular weight polymerhaving molecular weight about or greater than 2000 g/mol.
 8. The methodof claim 1, where the at least one additive comprises a high molecularweight polymer having a molecular weight about or greater than 10000g/mol.
 9. The method of claim 1, where the at least one additive isselected based on one or more of: a thickness of the first layer, thedielectric material, the filling material, a temperature used to heatthe structure and enable the filling material to at least partially fillthe plurality of pores, a heating time, and pore size of the pluralityof pores.
 10. The method of claim 1, where the at least one additivecomprises the surfactant.
 11. The method of claim 1, where the at leastone additive comprises the high molecular weight polymer.
 12. The methodof claim 1, where the at least one additive comprises a high boilingpoint solvent.
 13. The method of claim 1, where heating the structureresults in the residual filling material being uniformly left across anarea of the surface of the first layer.
 14. A method comprising:providing a structure comprising a first layer overlying a substrate,where the first layer comprises a dielectric material having a pluralityof pores; applying a filling material to a surface of the first layer,where the filling material comprises a polymer and at least oneadditive, where the at least one additive comprises at least one of asurfactant, a high molecular weight polymer and a solvent having aboiling temperature greater than 150° C., where the at least oneadditive is operable to raise a dewet start temperature of the fillingmaterial, where the dewet start temperature is a temperature at whichthe surface of the first layer begins to dewet, where the at least oneadditive is thermally removable, where the high molecular weight polymerhas a molecular weight about or greater than 2000 g/mol, where the atleast one additive is selected based on one or more of: a thickness ofthe first layer, the dielectric material, the filling material, atemperature used to heat the structure and enable the filling materialto at least partially fill the plurality of pores, a heating time, andpore size of the plurality of pores; and applying the filling material,heating the structure to enable the filling material to at leastpartially fill the plurality of pores uniformly across an area of thefirst layer, where heating the structure results in residual fillingmaterial being uniformly left on surface of the first layer.
 15. Themethod of claim 14, where the at least one additive is thermallyremovable.
 16. The method of claim 14, where heating the structureresults in the residual filling material being uniformly left across anarea of the surface of the first layer.